1. Field of the Invention
The present invention relates to a method of forming a temperature pattern with respect to time or progress in process of a heater for heating and melting silicon (Si) for use in a Si single crystal producing apparatus using the Czochralski method, and to a Si single crystal growth control apparatus using the temperature pattern.
2. Description of Prior Art
In recent years, with the high integration and the diversification of semiconductor devices, specifications on the quality of a semiconductor single crystal requested from device manufacturers have become diversified.
On the other hand, when a Si single crystal is pulled up from Si molten liquid in a quartz crucible in the Czochralski method, it is necessary to change various production conditions, such as the rotational speed of the crucible, the temperature of a heater and the pull-up speed and the rotational speed of a Si single crystal pulling shaft, in order to meet the specifications.
However, if one production condition is changed, since the change has a complicated influence on other production conditions, the control of the shape and quality of the Si single crystal becomes extremely complicated.
For example, if the rotational speed of the crucible is increased, the reaction between the Si molten liquid and the quartz crucible is increased and the amount of oxygen to be taken into the Si single crystal is increased. However, if the temperature of the Si molten liquid is raised, the reaction between the Si single crystal and the quartz crucible is also increased and the amount of oxygen to be taken into the Si single crystal is increased. Furthermore, if the rotational speed of the crucible is increased, the temperature of the growing portion of the Si single crystal is lowered by the convection of the Si molten liquid and the growing speed of the Si single crystal is increased. Furthermore, if the temperature of the Si molten liquid is lowered, the growing speed of the Si single crystal is increased and the diameter of the Si single crystal becomes longer. However, if the pull-up speed of the Si single crystal is decreased, the diameter of the Si single crystal also becomes longer.
Therefore, it is necessary to conduct the feedback of many experimental facts (enormous data) to the control through human judgement. This operation is troublesome and takes much time.
Although such a problem will be solved by using a non-Neumann neurocomputer in the future, it is not yet practical at present.